In a typical radio communications network, wireless terminals, also known as mobile stations, terminals and/or user equipments, UEs, communicate via a Radio Access Network, RAN, to one or more core networks. The radio access network covers a geographical area which is divided into cell areas, with each cell area being served by a base station or network node, e.g. a radio base station, RBS, which in some networks may also be referred to as, for example, “NodeB”, “eNB” or “eNodeB”.
A Universal Mobile Telecommunications System, UMTS, is a third generation mobile communication system, which evolved from the second generation, 2G, Global System for Mobile Communications, GSM. The UMTS terrestrial radio access network, UTRAN, is essentially a RAN using wideband code division multiple access, WCDMA, and/or High Speed Packet Access, HSPA, for user equipments. In a forum known as the Third Generation Partnership Project, 3GPP, telecommunications suppliers propose and agree upon standards for third generation networks and UTRAN specifically, and investigate enhanced data rate and radio capacity. In some versions of the RAN as e.g. in UMTS, several base stations may be connected, e.g., by landlines or microwave, to a controller node, such as a radio network controller, RNC, or a base station controller, BSC, which supervises and coordinates various activities of the plural base stations/network nodes connected thereto. The RNCs are typically connected to one or more core networks.
Specifications for the Evolved Packet System, EPS, have been completed within the 3rd Generation Partnership Project, 3GPP, and this work continues in the coming 3GPP releases. The EPS comprises the Evolved Universal Terrestrial Radio Access Network, E-UTRAN, also known as the Long Term Evolution, LTE, radio access, and the Evolved Packet Core, EPC, also known as System Architecture Evolution, SAE, core network. E-UTRAN/LTE is a variant of a 3GPP radio access technology wherein the radio base station nodes are directly connected to the EPC core network rather than to RNCs. In general, in E-UTRAN/LTE the functions of a RNC are distributed between the radio base stations nodes, e.g. eNodeBs in LTE, and the core network. As such, the Radio Access Network, RAN, of an EPS has an essentially flat architecture comprising radio base station nodes without reporting to RNCs.
In Dual Connectivity, DC, a communication device may be served by two or more network nodes. These are commonly referred to as main network node, MeNB, and secondary network nodes, SeNB. They may also be referred to as primary and secondary, or anchor and booster. The communication device is here configured with a Primary Component Carrier, PCC, from both MeNB and SeNB. The PCell from MeNB and SeNB are referred to as PCell and PSCell, respectively. The PCell and PSCell typically operate the communication device independently. The communication device may also be configured with one or more Secondary CCs, SCCs, from each of MeNB and SeNB. The corresponding secondary serving cells served by MeNB and SeNB are referred to as SCell. The communication device operating in DC typically has separate transmissions/receptions, TX/RX, for each of the connections with MeNB and SeNB. This allows the MeNB and SeNB to independently configure the communication device with one or more procedures, such as, e.g. radio link monitoring (RLM), DRX cycle, etc., on their PCell and PSCell, respectively. More specifically DC is a mode of operation of the communication device in RRC_CONNECTED state. In 3GPP TS 36.300, version 12.3.0, two options are defined for dual connectivity as follows. First, a “Secondary Cell Group (SCG) bearer” option is specified, which enables changing the U-plane termination point in the E-UTRAN by means of S1-MME signaling without changing the S1-MME termination point. Secondly, a “Split bearer” option is specified, wherein the “split bearer” in the E-UTRAN is transparent to the core network entities (e.g. MME, S-GW, etc.).
DC may improve the per-user throughput and would be of interest to operators and users.
In the existing 3GPP TS 23.007, version 12.6.0, there is a requirement for when an SGW receives a GTP error indication from an eNB, as follows:
“For an ‘Active’ mode UE having a user plane connection with an eNB, i.e. SGW has F-TEIDs assigned by eNB for user plane for the UE, when the SGW receives a GTP Error Indication for a Bearer Context from an eNodeB, the SGW should not delete the associated Bearer Context but delete all the eNodeB GTP-U tunnel TEIDs for this UE and sends a Downlink Data Notification message to the MME (the complete behaviour is specified in clause 22). Then the SGW starts buffering downlink packets received for this UE.
Correspondingly, the requirements for the MME are described in clause 22 of the existing 3GPP TS 23.007, version 12.6.0, as follows:
“If the UE is in CONNECTED state, upon receipt of the Downlink Data Notification message, the MME shall perform S1 Release procedure and perform Network Triggered Service Request procedure as specified in 3GPP TS 23.401 (version 12.6.0).”
However, this procedure may lead to significant signaling in the radio communications network. In particular, in case the nodes in the radio communications network are operating in a Dual Connectivity, DC, mode. Hence, an improved way of signaling in the radio communications network is needed.